In the field of patient monitoring, assemblies comprising a medical main device, for example, a measurement device, and one or more accessories devices, for example, cables and sensors, are adapted to conduct measurements at the specific location at the patient. Cables and sensors are often designed for one time use or need to be cleaned or sterilised after usage. Therefore, these accessories must be detachable from the main device. A connector provides mechanical stability and electrical connections for data or power flow or material flow from the accessory to the measurement device.
It is known to use plug and socket arrangements for mechanical and electrical connection. Typically connectors are build and optimized for different purposes: providing a detachable mechanical joint, providing mechanical stability when connected, protecting electrical contacts from environmental conditions (humidity, dirt, corrosion, destruction), and protecting a person from potential harm caused by touching electrical contacts. In the field of medical devices the last point needs special attention. A patient or person might not be able to disengage himself from a hazardous device. During surgery exposed tissue might be more vulnerable than usual. Legal regulations for medical devices covering this topic must be obeyed.
U.S. Pat. No. 6,902,412 B2 discloses an assembly, comprising a mobile phone and an accessory connectable to the mobile phone. The mobile phone and the accessory each comprise a supply contact and a detect contact. If disconnected, no voltage is applied at the supply contact of the main device. If connected, a voltage is applied at the supply contact of the main device, supplying the accessory with electric power. The different states are detected by a detection circuit of the mobile phone. A low voltage is applied at the detect contact of the main device. While connecting the accessory to the mobile phone, the accessory detect contact touches the detect contact of the main device, leading to a change of logic state inside the detection device, which enables applying a voltage at the supply contact. The supply contact of the accessory is longer than the detect pin, so that the supply contacts are touching each other before the detect contacts are getting into contact. Therefore, voltage is applied at the supply contact only after the supply contacts are in contact, minimizing or preventing the causing of sparks.
However, known methods for detecting an accessory have several disadvantages. Environmental conditions (water, moisture, dirt) can disturb the quality and reliability of the method. Furthermore, mechanical deformations, accidental or willing misuse can lead to false detection.